Two studies are proposed to examine electrophysiological and neuropsychological test performance in recovering substance abusers. Study #1 will examine 30 cocaine dependent and 30 alcohol dependent patients after 2-4 and 8-10 months of verified abstinence. Study #2 will examine 2 groups of methadone-maintained patients with recent (2-4 months) or without histories of cocaine dependence. As a secondary goal, Study #2 will also compare methadone-dependent patients in the early asymptomatic stages of HIV-1 infection of those without infection. It will also allow examination of the potential additive or interactive effects of current HIV infection and previous cocaine dependence. The test battery will include several measures from our current battery, e.g., tremor, smooth pursuit and saccadic eye movements, EEG photic driving responses. Several new measures will also be added to assess sensory function (SEP, ABR, PRVEP) and higher level cognitive abilities, such as cognitive flexibility and short term memory. The same measures will be recorded from groups of non-drug-dependent, age- and education- matched controls. The resultant data will be useful for describing the nature, severity, and persistence of neuropsychological/electrophysiological impairments in recovering cocaine dependent patients. The data will also identify subgroups of cocaine dependent patients who may be at greatest neuropsychological risk, due to opiate dependence and/or HIV infection.